Social Significance of the Eyebrows and Periorbital Complex
January 2014 | Volume 13 | Issue 1 | Supplement Individual Articles | 7 | Copyright © January 2014
Jean Carruthers MD FRCSC FRC (OPHTH)a and Alastair Carruthers MD MRCP FRCPCb
aDepartment of Ophthalmology and Visual Sciences, University of British Columbia, Vancouver, Canada
bDepartment of Dermatology and Skin Science, University of British Columbia, Vancouver, Canada
The eyebrow is simple to regard, but complicated to understand. Over the centuries it has been used as an indicator of social status, gender, and level of authority. In differing societies its descent and thinning with time have made it an important benchmark of the aging process. The brow is higher in the younger woman, but because of the loss of periorbital bone and fat starting in early middle age in women, the brow tends to descend, giving a tired, depressed, or anxious appearance. The brow in men is usually more resistant to downward movement until they are in their fifties. As a result, a whole industry has grown up around such varied techniques as plucking and redrawing, or gluing or tattooing on a replacement. In earlier centuries, the shaven forehead and almost absent brow were seen as a symbol of sexual purity. In the modern age, the brow is seen as an important part of facial recognition technology and is valuable in aspects of security and monitoring. J Drugs Dermatol.
If the eyes are the windows to the soul, the eyebrows must surely be the frames, shaping the face and giving definition to the eyes and forehead. Many women spend a great deal of time maintaining the appearance of the eyebrows, via plucking and shaping, cosmetics, or even surgical implants. Historically, fashionable trends revolved around thickness, hue, and the shape of the arch; and there is no doubt that eyebrows have always contributed significantly to the perception of facial attractiveness.
However, compared with other primates, modern humans are relatively hairless, so the persistence of the eyebrow over time is curious.1 Do eyebrows merely represent evolutionary vestiges, or do they serve a greater, or more functional, purpose? Indeed, as one of the most powerful and versatile features of the human face, the eyebrow informs the perception of beauty and plays a critical role in sexual dimorphism, facial recognition, and non-verbal communication.
Muscular Anatomy of the Brow
The musculature of the brow has received intense study with the advent of brow treatments with neuromodulators and fillers. Three muscles—the corrugator supercilii, procerus, and depressor supercilii—work together to cause the head of the brow to rotate medially and descend in the frown.2 The frontalis, the primary elevator muscle, raises the forehead and eyebrows medially and can elevate the eyelid as high as 5 mm at maximal action.3 (Figure 1).
From the age of 25 in women and 45 in men, there is a progressive resorption of bone and fat in the periocular and perioral regions.4 For the first time in history, brow position can be affected by voluntary medical injection treatments,5 a trend that is summarized by the 4900.1% increase in injectable treatments seen from 1997 to 2012.6 (Figures 2a and 2b.)
Evolution of the Brow
The supraorbital ridge, also called the supraorbital arch or supraciliary ridge, lies above the eye sockets and is common to all primates, including humans, although the size of the ridge varies between species.7 Scientists refer to a more prominent ridge as the supraorbital torus, which presents as a continuous shelf of bone that projects above the orbits and nose and can be seen in our closest living relatives (the gorilla and chimpanzee), as well as in most fossil hominids (our ancestors). With the expansion of the cortex and development of the frontal lobe, the prominent brow gave way to the high, straight forehead of modern Homo sapiens, leaving behind only 2 hairy reminders of our evolutionary past along the lower margins of the ridge. What purpose do they serve?
Researchers believe the primary function of the eyebrow to be one of protection, the slope of the brow and arch drawing moisture or other debris around to the sides of the face. Because of their position and curvature, the eyebrows act as a shield against direct bright light, and stimulation of the hairs—abundantly innervated and sensitive to tactile stimulation—causes a reflex blinking of both eyelids.8 But why did